Oxygen Reduction Reaction Electrocatalytic Performance Analysis of Annealed Vitamin B12 Coupled with Carbon Nanotube
CHINESE JOURNAL OF ANALYTICAL CHEMISTRY
Authors: Duan Guang-Bin; Fang Ya-Ting; Dong Kai; Jiang Yuan-Yuan; Chen Chuan-Xia; Ni Peng-Juan; Lu Yi-Zhong
In the research of fuel cells , the development of cathode oxygen reduction electrocatalysts with low cost and high performance to replace platinum based catalyst is a critical path of realizing the commercialization of fuel cell. Carbon nanomaterials supported transition metal macrocyclic compounds have many advantages including low cost , high activity , strong catalytic selectivity , good electrical conductivity and high stability . Herein , the CNT-VB12 composite was prepared based on the Co-Nx center structure of Vitamin B12 ( VB12 ) through high temperature pyrolysis and with VB12 as the active sites precursor and carbon nanotubes as carrier . We characterized the morphology and the composition of the as-prepared composite , and analyzed its electrocatalytic activity , stability , selectivity and the anti-interference performance for oxygen reduction reaction ( ORR ) . The results showed that the CNT-VB12 exhibited high ORR electrocatalytic activity in alkaline electrolyte (0. 1 mol/L KOH) . The corresponding electron transfer number was calculated to be close to 4 , which suggested that the electrocatalyst reduced O-2 predominately to H2O . Moreover , the synthesized CNT-VB12 electrocatalyst outperformed commercial Pt/C in terms of better methanol tolerance and stability . All these performance made this CNT-VB12 composite very promising non-precious metal ORR electrocatalyst for practical fuel cell application .
A LC/UV/Vis method for determination of cyanocobalamin (VB12) in multivitamin dietary supplements with on-line sample clean-up
Authors: Chen, Pei; Wolf, Wayne R.; Castanheira, Isabel; Sanches-Silva, Ana
A HPLC-UV/Vis method using a two-column strategy with a switching valve for on-line sample cleanup was developed for the determination of cyanocobalamin (CN-Cbl/Vitamin 1312) in multivitamin dietary supplement tablets. The method uses two columns: an Agilent Zorbax C8 (150 mm x 4.6 mm, 5 mu m particle size) reversed-phase column and a Waters Symmetry C18 (150 mm x 4.6 mm, 5 mu m particle size) reversed-phase column. Chromatographic separation was achieved using a programmed gradient mobile phase consisting of (A) 0.1% formic acid in water and (B) 0.1% formic acid in acetonitrile. Because of the low levels of Vitamin B-12 in the samples, large injection volumes, and thus much interfering material, must be used to exceed the limit of quantitation (LOQ) by UV detection. A switching valve was used to divert most of these early eluting interfering materials to waste, effecting on-line sample clean-up without excessive sample preparation steps. The recovery of CN-Cbl in the method was 99.5% and the LOQ was 10 ng per injection. The method was successfully applied to the analysis of the NIST SRM 3280 multivitamin/multimineral dietary supplement tablet. The method is specific, precise, and accurate for the intended use. Compared to off-line sample clean-up procedures, it offers the advantage of being easier, more economical, and less time-consuming.